Pre-pregnancy BMI, rate of gestational weight gain, and preterm birth among US Pacific Islander individuals.

Objective: The objective of this study was to examine the association between rate of gestational weight gain (GWG) and preterm birth (PTB) classified by pre-pregnancy BMI among Pacific Islander individuals in the United States.

Methods: Pacific Islander mothers (n = 55,975) and singleton infants (22-41 gestational weeks) without congenital anomalies were included using data from the National Center for Health Statistics (2014-2018). PTB was compared by pre-pregnancy BMI among women in each stratum of rate of GWG using Cox proportional hazards models.

Results: Compared with mothers with a rate of GWG within the guidelines, mothers with a rate of GWG below the guidelines and either pre-pregnancy underweight (adjusted hazard ratio [aHR] = 1.84, 95% CI: 1.10-3.06), healthy weight (aHR = 1.38, 95% CI: 1.15-1.65), obesity class I (aHR = 1.22, 95% CI: 0.97-1.52), or obesity class II (aHR = 1.43, 95% CI: 1.05-1.96) had an increased risk of PTB; mothers with a rate of GWG above the guidelines and either pre-pregnancy underweight (aHR = 1.57, 95% CI: 0.92-2.69) or obesity class II (aHR = 1.31, 95% CI: 0.98-1.76) had an increased risk of PTB.

Conclusions: The association between rate of GWG below or above the guidelines and PTB differs by pre-pregnancy BMI among Pacific Islander individuals.